Jet2 website says passengers on affected BLK return flights after 15th October will be flown back to MAN, so, one could assume that the 2 B737's will be based at MAN initially to bring the passengers home.
Afterwards, Im assuming that the 2 aircraft will be used as spares given that Jet2 are still hiring in other aircraft (privilege currently operating at LBA), or, possibly run extra flights from say, MAN, depending on what the BLK passengers want to do for departures after 15th Oct (ei do they want to still fly or opt for a refund).